A collapsible, self-expanding polyhedron comprises a plurality of side members each connected with an elastic band that is sized to urge each side wall of adjacent side members together to form an expanded configuration. When the polyhedron is compressed on two opposing side members, which causes the other side members to separate into a collapsed configuration, the elastic band expands to a maximum length with maximum tension. Once the compression is released, the at least one elastic band retracts back to a minimum length and urges the side members back into the expanded configuration.